=item *
-$E<lt>I<digit>E<gt> does not refer to fields--it refers to substrings matched
+$<I<digit>> does not refer to fields--it refers to substrings matched
by the last match pattern.
=item *
The concatenation operator is ".", not the null string. (Using the
null string would render C</pat/ /pat/> unparsable, because the third slash
would be interpreted as a division operator--the tokenizer is in fact
-slightly context sensitive for operators like "/", "?", and "E<gt>".
+slightly context sensitive for operators like "/", "?", and ">".
And in fact, "." itself can be the beginning of a number.)
=item *
=item *
-C<printf()> does not implement the "*" format for interpolating
-field widths, but it's trivial to use interpolation of double-quoted
-strings to achieve the same effect.
-
-=item *
-
Comments begin with "#", not "/*".
=item *
=item *
-The E<lt>FHE<gt> construct is not the name of the filehandle, it is a readline
+The <FH> construct is not the name of the filehandle, it is a readline
operation on that handle. The data read is assigned to $_ only if the
file read is the sole condition in a while loop:
=back
If you find an example of a conversion trap that is not listed here,
-please submit it to Bill Middleton <F<wjm@best.com>> for inclusion.
-Also note that at least some of these can be caught with B<-w>.
+please submit it to <F<perlbug@perl.org>> for inclusion.
+Also note that at least some of these can be caught with the
+C<use warnings> pragma or the B<-w> switch.
=head2 Discontinuance, Deprecation, and BugFix traps
$a=1;$b=2;$c=3;$var=4;
print "$a::$b::$c ";
print "$var::abc::xyz\n";
-
+
# perl4 prints: 1::2::3 4::abc::xyz
# perl5 prints: 3
# perl4 prints: second new
# perl5 prints: 3
-=item * Discontinuance
-
-In Perl 4 (and versions of Perl 5 before 5.004), C<'\r'> characters in
-Perl code were silently allowed, although they could cause (mysterious!)
-failures in certain constructs, particularly here documents. Now,
-C<'\r'> characters cause an immediate fatal error. (Note: In this
-example, the notation B<\015> represents the incorrect line
-ending. Depending upon your text viewer, it will look different.)
-
- print "foo";\015
- print "bar";
-
- # perl4 prints: foobar
- # perl5.003 prints: foobar
- # perl5.004 dies: Illegal character \015 (carriage return)
-
-See L<perldiag> for full details.
-
=item * Deprecation
Some error messages will be different.
=item * Discontinuance
+In Perl 4, if in list context the delimiters to the first argument of
+C<split()> were C<??>, the result would be placed in C<@_> as well as
+being returned. Perl 5 has more respect for your subroutine arguments.
+
+=item * Discontinuance
+
Some bugs may have been inadvertently removed. :-)
=back
Also see L<"General Regular Expression Traps using s///, etc.">
for another example of this new feature...
+=item * Bitwise string ops
+
+When bitwise operators which can operate upon either numbers or
+strings (C<& | ^ ~>) are given only strings as arguments, perl4 would
+treat the operands as bitstrings so long as the program contained a call
+to the C<vec()> function. perl5 treats the string operands as bitstrings.
+(See L<perlop/Bitwise String Operators> for more details.)
+
+ $fred = "10";
+ $barney = "12";
+ $betty = $fred & $barney;
+ print "$betty\n";
+ # Uncomment the next line to change perl4's behavior
+ # ($dummy) = vec("dummy", 0, 0);
+
+ # Perl4 prints:
+ 8
+
+ # Perl5 prints:
+ 10
+
+ # If vec() is used anywhere in the program, both print:
+ 10
+
=back
=head2 General data type traps
=item * (SysV)
-Under SysV OSes, C<seek()> on a file opened to append C<E<gt>E<gt>> now does
+Under SysV OSes, C<seek()> on a file opened to append C<<< >> >>> now does
the right thing w.r.t. the fopen() manpage. e.g., - When a file is opened
for append, it is impossible to overwrite information already in
the file.
print "To: someone@somewhere.com\n";
# perl4 prints: To:someone@somewhere.com
- # perl5 errors : In string, @somewhere now must be written as \@somewhere
+ # perl < 5.6.1, error : In string, @somewhere now must be written as \@somewhere
+ # perl >= 5.6.1, warning : Possible unintended interpolation of @somewhere in string
=item * Interpolation
https://perl5.git.perl.org / perl5.git / blobdiff